The present invention relates generally to automotive lamps. In particular, the present invention relates to an assembly for moving the light beam pattern of a headlamp.
Generally, conventional automotive headlamps utilize a reflector of parabolic shape and an incandescent lamp. However, a projector headlamp, which has recently come into use more widely in the United States, is an automotive headlamp that typically utilizes a reflector of elliptical shape and may include a high intensity discharge gas lamp. A projector headlamp also generally requires the use of a condensing lens, which is located in front of the lamp and the reflector, to focus the light emitted by the assembly into a concentrated beam pattern which meets applicable automotive lighting requirements.
In response to changing driving conditions, it can become desirable to move the beam pattern relative to the vehicle. For example, when a vehicle is being driven around a corner, it may be desirable for the beam pattern of that vehicle""s forward lighting system to be adjusted, axially and/or laterally, such that the emitted light better illuminates the area in the direction the vehicle is turning. Additionally, adverse weather conditions or an increase or decrease in a vehicle""s speed may also result in circumstances where adjustment of the vehicle""s forward lighting beam pattern may become desirable. Automotive headlamps that can be adjusted in this manner are generally known in the industry as adaptive front lighting systems (xe2x80x9cAFSxe2x80x9d).
AFS for projector headlamps are generally known in the art. Such systems generally move the emitted light beam pattern by moving the entire projector headlamp assembly. For example, U.S. Pat. No. 6,186,651 (the xe2x80x9c""651 patentxe2x80x9d) discloses the use of solenoids, motors, cams and such to move the reflector, condenser lens and light shield of the projector headlamp assembly. This method, however, has some significant disadvantages. For example, laterally moving the entire projector lamp distorts the assembly""s beam pattern from its original shape. This can cause the emitted light to become noncompliant with applicable government regulations. Additionally, moving the entire projector lamp requires a large amount of space behind the headlamp to keep the headlamp from swinging into other parts. An additional shortcoming of this approach is that moving the whole assembly requires at least some movement of electrical wires that supply power to the light source. Such movement can eventually result in a complete failure of the assembly. Moreover, when adjustments in the light""s beam pattern are necessary, moving the large mass of the entire headlamp requires a longer than ideal response time or a larger and less efficient means for moving the assembly.
It is also generally known to pivot the condenser lens in order to adjust the aim point of the headlamp assembly in the vertical plane. For example, the ""651 patent discloses the use of a pivoting condensing lens in conjunction with a pivoting light shield to allow for a single headlamp assembly to provide illumination for both low beam and high beam conditions. While useful for small adjustments in aiming, such as when shifting between low beam illumination and high beam illumination, pivoting the condensing lens around an axis results in unacceptable levels of beam distortion for angles which are desired when a vehicle is turning.
It is also generally known to move a condenser lens within a plane that is perpendicular to the horizontal axis of the headlamp. Such a system is disclosed in U.S. Pat. No. 5,915,829 (the xe2x80x9c""829 patentxe2x80x9d). According to the ""829 patent, a lens is mounted within two mountings, both of which are in a plane perpendicular to the horizontal headlamp axis. These mountings are then used to move the lens within the plane perpendicular to the horizontal headlamp axis, so as to control the position of the light beam of the headlight assembly. Although the system disclosed in the ""829 patent does allow for some horizontal displacement of a light beam, it is of limited usefulness when a vehicle is turning. Another disadvantage of this system is that as the lens is moved within the mountings, the incidence angle of the light striking the lens increases, causing undesired distortion of the light beam formed by the lens. Thus, the angular displacement of the light beam is limited.
Therefore, it is desirable to provide a headlamp assembly that allows for significant angular displacement of the light beam of a headlamp assembly without excessive light beam distortion and without the need to move the entire headlamp assembly. It is further desired that the system be of inexpensive and dependable construction. It is further desired that the headlamp assembly be easily configured to fit within space confines of a variety of vehicle designs.
In accordance with the present invention, a headlamp assembly is provided which overcomes the disadvantages of the prior art by providing a condenser lens that is movable along an arcuate path. One exemplary embodiment of the invention comprises an elliptical reflector having two focal points. A light source is located proximate to the first focal point, and a condenser lens is rotatable around the second focal point. As a vehicle turns, the condenser lens is moved along an arcuate path such that the light beam formed by the headlamp assembly is projected in the direction which the vehicle is turning.
The invention provides a headlamp assembly that allows for significant angular displacement of the light beam of a headlamp assembly without excessive light beam distortion and without the need to move the entire headlamp assembly. The invention further provides a headlamp assembly which is inexpensive and of dependable construction. Moreover, it is advantageous that a headlamp assembly according to the present invention can be easily configured to fit within space confines of a variety of vehicle designs.